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Virtu Ost VFA uses sagittal sections from a spine-containing CT scan, with or without contrast enhancement, to visualize and measure vertebral deformities, classify the type and grade of any existing vertebral fracture, and from this identify patients at high risk of a future osteoporosis-related fracture. This information can be interpreted by a physician to diagnose existing vertebral fractures and to manage patients for osteoporosis.

VirtuOst Vertebral Fracture Assessment (VFA) software is used to perform vertebral morphometry and is an integrated component of VirtuOst (K113725). VirtuOst VFA accepts as input a sagittal section of a vertebral body, obtained from a spine-containing computed tomography (CT) scan, and provides semi-automated, interactive tools with which the user can perform six-point quantitative vertebral morphometry according to well-established guidelines. The process can be repeated for multiple vertebral bodies. For each vertebral body analyzed, the quantitative vertebral morphometry algorithm locates three points each along the superior and inferior endplate on a sagittal section through the vertebra, typically a mid-sagittal section. The user verifies or modifies point placement. Based on these six morphometry points, anterior, posterior and middle vertebral heights are measured. Percent deformities are calculated from these heights and are then compared against well-established criteria for vertebral deformities typical of osteoporosis-related vertebral fracture in order to classify types and grades of any existing osteoporosis-related vertebral fracture, from which a patient can be classified as being at high risk of a future osteoporosis-related fracture. The VFA algorithm can be applied to any complete vertebral body captured in the CT scan, and the scan can be contrast-enhanced or not. Consistent with the recommended use of the well-established fracture-classification criteria, deformity types and fracture grades and fracture-risk classifications are only reported for vertebral levels T4 through L4. A report is generated containing these results, along with images of the sagittal sections from which the measurements were acquired. A physician then interprets the report to make any medical diagnoses or treatment decisions.

Here's a breakdown of the acceptance criteria and the study details for the VirtuOst Vertebral Fracture Assessment device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state quantitative acceptance criteria in percentages or thresholds in a dedicated section. However, it implicitly uses agreement and precision metrics compared to manual measurements and a predicate device as evidence of acceptable performance for market clearance.

Summary of Device Performance: The study concludes that VirtuOst VFA is highly accurate, and its precision is substantially equivalent to that of the predicate device. Precision errors are small and do not significantly affect fracture determination or grading, even with varying CT slice thicknesses (up to 3mm) and the use of IV contrast enhancement.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: n=40 women and men (35 with potential fractures, 5 without).
• Data Provenance:
  • Country of Origin: Not explicitly stated, but the study used "computed tomography scans acquired as part of standard care for 7000 women and men age 65 and older."
  • Retrospective or Prospective: The selection of patients from an existing database of 7000 CT scans, where scans were within a 90-day period (implying existing sets of scans), indicates a retrospective study design for data collection.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

• Number of Experts: Not explicitly stated. The text mentions "vertebral heights were also manually measured from high resolution (0.5 mm) printouts of midsagittal sections of the L1 vertebra from each CT scan." It does not specify who performed these manual measurements or their qualifications. It simply refers to these "manual measurements" as the reference standard.

4. Adjudication Method for the Test Set

• Adjudication Method: Not explicitly described. The manual measurements are presented as a reference standard, but the process by which multiple experts might have agreed upon these measurements (e.g., 2+1, 3+1) is not detailed. The study mentions two operators performing VFA, but this is for repeatability analysis of the device, not for establishing ground truth directly.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• Was an MRMC study done?: No. The study conducted was primarily a precision and accuracy study, comparing the device's measurements against manual measurements and assessing intra- and inter-operator variability. It did not involve comparing human readers' diagnostic performance with AI assistance versus without AI assistance.

• Effect size of human reader improvement with AI vs. without AI assistance: Not applicable, as no MRMC comparative effectiveness study was performed in this manner.

6. Standalone Performance Study

• Was a standalone study done?: Yes. The study investigated the "Accuracy of VirtuOst VFA relative to the manual measurements" and its repeatability (intra-operator, interoperator, short-term, combined precision), as well as the impact of slice thickness and contrast enhancement on the device's performance. This directly assesses the algorithm's performance independent of real-time human interpretation loop changes in diagnostic workflow.

7. Type of Ground Truth Used

• Ground Truth Type: "Manual measurements" of vertebral heights from high-resolution printouts of midsagittal sections using six-point morphometry methods. This constitutes an expert-derived or reference standard measurement based on established definitions of vertebral fracture. The specific "experts" who performed these manual measurements are not explicitly qualified in the text.

8. Sample Size for the Training Set

• Sample Size for Training Set: Not specified. The document focuses on the validation study and does not provide details about the training data used to develop the VirtuOst VFA algorithm.

9. How the Ground Truth for the Training Set Was Established

• How Ground Truth for Training Set Was Established: Not specified in the provided text.

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